Various processes for the alkylation of olefins employing alkali metal catalysts alone or supported on suitable carriers, together with certain promoters have previously been reported. U.S. Pat. No. 2,492,693 discloses the use of an alkali metal (sodium) catalyst and a polynuclear aromatic hydrocarbon promoter for the intermolecular condensation of different monoolefins. In the Journal of American Society, vol. 77, pp. 554-559 (1955), the reaction of alkyl aromatic compounds with ethylene takes place in the presence of a sodium catalyst and an organic compound promoter. British Patent No. 2,269,280 discloses alkylating an aromatic hydrocarbon with a monoolefin in the presence of a catalyst prepared by dispersing an alkali metal on a potassium compound. U.S. Pat. No. 4,511,748 discloses a process for alkylating aromatic hydrocarbons with olefins using a catalyst comprising sodium and/or sodium amide on a potassium carbonate carrier.
Other known process for the dimerization of olefins employing potassium as catalyst component are found in U.S. Pat. No. 3,175,020, which discloses catalysts having potassium metal on a alumina carrier; and U.S. Pat. Nos. 4,609,637, 4,661,466, 4,544,790 and 4,505,787 which teach the use of elemental alkali metals deposited on potassium carbonate catalyst supports.
U.S. Pat. No. 3,651,161 discloses a process for the alkylation of compounds with an active hydrogen, allylic or benzylic, and the use of sodium/pyrene charge transfer complex or a potassium/biphenyl charge transfer complex.
It has now been found that a catalyst comprising an alumina having a sodium content per unit surface area of less than about 3.times.10.sup.-5 g/m.sup.2, when properly activated, promotes an ethylation reaction in which ethylene is added to detergent-range olefins to produce more-branched olefins of higher molecular weight.